Two Professor Challenger adventures chronicle--respectively--the professor's expedition to an ancient world inhabited by dinosaurs and ape-men, and his plan to save the world from the deadly gas he prophesies

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From the Publisher:

This book is a standard print version using a minimum of 10 point type in a 6 by 9 inch size and perfect bound - a paperback. As with all Quiet Vision print books, it use a high grade, acid free paper for long life.